Your system may not meet the requirements for Firefox, but you can try one of these versions:

Your system doesn't meet the requirements to run Firefox.

Your system doesn't meet the requirements to run Firefox.

Please follow these instructions to install Firefox.

Firefox Privacy Notice

Mozilla Foundation Security Advisory 2011-43

loadSubScript unwraps XPCNativeWrapper scope parameter

September 27, 2011
David Rees
Firefox, SeaMonkey
Fixed in
  • Firefox 7
  • SeaMonkey 2.4


David Rees reported that the JSSubScriptLoader (a feature used by some add-ons) was "unwrapping" XPCNativeWrappers when they were used as the scope parameter to loadSubScript(). Without the protection of the wrappers the add-on could be vulnerable to privilege escalation attacks from malicious web content. Whether any given add-on were vulnerable would depend on how the add-on used the feature and whether it interacted directly with web content, but we did find at least one vulnerable add-on and presume there are more.

The unwrapping behavior was a change introduced during Firefox 4 development. Firefox 3.6 and earlier versions are not affected.